Many people suffer from what is called “Dry Eye”. In which case the patient's eyes feel tired, scratchy or as though there were something grainy in them. The most common cause of dry eyes or tear dysfunction is due to aqueous deficiency and is best represented by Sjogrenis syndrome. Dry eyes tend to point to the insufficient production, distribution or retention of the tears. Naturally the tears need to be evenly retained and distributed across the corneal surface of the eye.
Natural tears are secreted by the lachrymal gland, which is located in the lateral orbit, and are evenly spread across the corneal surface of the eye and finally get excreted from the tear ducts (lachrymal puncti) to the nasolateral ducts which lead into the nose as illustrated in FIG. 1. The opening from the eye to the tear ducts is called the punctum, and the place which the tears get excreted from the eye. Movement of the eyelids helps distribute the tear across the eye.
The natural tear film consists of three layers, aqueous, mucin and lipid. The outer most layer is lipid, and comes from the meibomian gland. The middle aqueous layer is composed of water-soluble substances and comes mainly from the major and minor lachrymal glands, but also from accessory glands called glands of Krauss and Wolfring. The inner most layer is a mucinous layer is secreted by the globlet cells of the conjunctiva and from the lachrymal gland, this layer is composed of glycoproteins.
The mucin layer lies over the corneal and conjunctival epithelial cells.
The epithelial cell membrane is composed of lipoproteins and thus is hydrophobic. This hydrophobic environment is difficult to wet. Thus the presence of the mucin layer is to provide a hydrophilic surface for which the middle aqueous layer can now wet. The outer lipid layer is believed to prevent evaporation of the middle aqueous layer.
There are a variety of current treatments, and such treatment of dry eyes varies with the severity of the disease. For patients with slightly dry eyes, the use of drops in bottles should be sufficient, for those with moderate dry eyes the use of gels may be necessary, and finally for those experiencing severe dry eyes gels, ointments or minor surgery to occlude the tear duct may be needed.
Drops are simple salt solutions with additional ingredients that help them spread across the eye. The drops lubricate the eye making it feel better, but the effect is short lived and there is a need to reapply the drops often (about four times daily). This method of treatment is not very effective for overnight use and the patient tend to wake up with dry sore eyes. There are several different types of drops available on the market, examples of trade name products include, “Liquifilm”, “Tears Natural”, “Hypomellose”, and “Snotears”.
Tear drop preparations without preservatives (also called preservative free) do not contain preservatives and so can be used a lot more regularly then other types of drops without causing any type of toxicity or reaction secondary to the preservatives. “Minims” tears are drops contained within a small ampoule; this carries about 14 drops and may last a patient a full day with proper use. These are moderately expensive.
The use of gels to treat dry eyes is fairly new, the two types available under trade names are “Gel Tears” and “Viscotears”. These last longer than drops and can be used for overnight treatment.
Ointments last even longer then gels. However, they may cause misty vision during the day if the treatment is applied at night. The two examples for this are “Simple” eye ointment and “lacrilube”.
There is no cure for dry eyes yet and so the only treatment is to use one of the above-mentioned methods to lubricate, or keep the eye oily. These methods are not harmful to the eye, but are a hassle to the patient. The constant need to apply drops, gels or ointments is very inconvenient and for the elderly with shaky hands it is a challenge. These types of treatments are also very expensive.
While, drops, gels and ointments are available for the treatment of dry eye, the repetitive need for re-application makes them not only inconvenient to use but also an added challenge for many with unstable hands.
Accordingly it is an object of this invention to provide an improved dry eye treatment.
Another object is to provide a dry eye treatment that is relatively inexpensive.
Yet another object of this invention is to provide a dry eye treatment that is long lasting and easy to apply.
Other objects will appear hereinafter.